Title: CSS Text Decoration Module Level 3
Shortname: css-text-decor
Level: 3
Status: ED
Work Status: Testing
Group: csswg
ED: https://drafts.csswg.org/css-text-decor-3/
TR: https://www.w3.org/TR/css-text-decor-3/
Previous Version: https://www.w3.org/TR/2018/CR-css-text-decor-3-20180703/
Previous Version: https://www.w3.org/TR/2013/CR-css-text-decor-3-20130801/
Previous Version: https://www.w3.org/TR/2013/WD-css-text-decor-3-20130103/
Previous Version: https://www.w3.org/TR/2012/WD-css-text-decor-3-20121113/
Editor: Elika J. Etemad / fantasai, Apple, http://fantasai.inkedblade.net/contact, w3cid 35400
Editor: Koji Ishii, Google, kojiishi@gmail.com, w3cid 45369
Implementation Report: https://wpt.fyi/results/css/css-text-decor
Abstract: This module contains the features of CSS relating to text decoration, such as underlines, text shadows, and emphasis marks.
At Risk: The ability to place both emphasis marks and ruby on the same base text.
Link Defaults: css-color-3 (property) color

spec:css-break-3; type:dfn; text:fragment
spec:css-display-3; type:property; text:display

Introduction

This subsection is non-normative. This module covers text decoration, i.e. decorating the glyphs of the text once typeset according to font and typographic rules. (See [[CSS-TEXT-3]] and [[CSS-FONTS-3]].) Such features are traditionally used not only for purely decorative purposes, but also in some cases to show emphasis, for honorifics, and to indicate editorial changes such as insertions, deletions, and misspellings. CSS Levels 1 and 2 only defined very basic line decorations (underlines, overlines, and strike-throughs) appropriate to Western typographical traditions. Level 3 of this module adds the ability to change the color, style, position, and continuity of these decorations, and also introduces emphasis marks (traditionally used in East Asian typography), and shadows (which were proposed then deferred from Level 2).

Module Interactions

This module replaces and extends the text-decorating features defined in [[!CSS2]] chapter 16.

Value Definitions

This specification follows the CSS property definition conventions from [[!CSS2]] using the value definition syntax from [[!CSS-VALUES-3]]. Value types not defined in this specification are defined in CSS Values & Units [[!CSS-VALUES-3]]. Combination with other CSS modules may expand the definitions of these value types. In addition to the property-specific values listed in their definitions, all properties defined in this specification also accept the CSS-wide keywords as their property value. For readability they have not been repeated explicitly.

Terminology

The terms character, letter, and content language as used in this specification are defined in [[!CSS-TEXT-3]]. Other terminology and concepts used in this specification are defined in [[!CSS2]] and [[!CSS-WRITING-MODES-4]].

Line Decoration: Underline, Overline, and Strike-Through

The following properties describe line decorations that are added to the content of an element. When specified on or propagated to an inline box, that box becomes a decorating box for that decoration, applying the decoration to all its fragments. The decoration is then further propagated to any in-flow block-level boxes that split the inline (see CSS2.1 section 9.2.1.1). When specified on or propagated to a block container that establishes an inline formatting context, the decorations are propagated to an anonymous inline box that wraps all the in-flow inline-level children of the block container. When specified on or propagated to a ruby container, the decorations are propagated only to the ruby base. For all other box types, the decorations are propagated to all in-flow children.

Note that text decorations are not propagated to any out-of-flow descendants, nor to the contents of atomic inline-level descendants such as inline blocks and inline tables. They are also not propagated to inline children of inline boxes, although the decoration is applied to such boxes. Underlines, overlines, and line-throughs are drawn only for non-replaced inline boxes, and are drawn across all text (including white space, letter spacing, and word spacing) except spacing (white space, letter spacing, and word spacing) at the beginning and end of a line. Atomic inlines, such as images and inline blocks, are not decorated. Margins, borders, and padding of the [=decorating box=] are always skipped, however the margins, border, and padding of descendant inline boxes are not.

Note that CSS 2.1 required skipping margins, borders, and padding always. In this level, by default only the margins, borders, and padding of the [=decorating box=] are skipped. In the future CSS2.1 may be updated to match this new default. Also, control over decorating leading/trailing spaces is expected in Level 4, and will be applied by default to the HTML <{ins}> and <{del}> elements. UAs may interrupt underlines and overlines where the line would cross glyph ink and to some distance to either side of the glyph outline; this behavior is not controllable in this level, but will be further defined in Level 4. Line-throughs must remain continuous, however.

An alphabetic underline through Myanmar text skips around descenders and the vertical strokes of combining characters that drop below the alphabetic baseline.

Skipping Glyph Ink

When the UA interrupts underlines or overlines at glyph boundaries, the shape of the line at that boundary should follow the shape of the glyph.

Note, this specification intentionally does not mandate a particular method for “following the shape” of the glyph so that UAs can take appropriate measures to handle aesthetic and performance considerations. For example, a UA could assume square line endings below a certain size threshold for performance reasons; or use trapezoidal endings to approximate curves, especially on thinner line decorations. In terms of aesthetic considerations, the UA might also consider what happens when the glyph boundary intersects only part of the line thickness or is slanted close to the horizontal-- following the curve exactly could result in typographically-awkward wisps of underline. Whether to show the line within enclosed areas of a glyph is yet another consideration.

Take, for example, the word “goal” with an underline striking through the bottom loop of the “g”.
Depending on the position and thickness of the underline,
we might see the entire thickness of the underline, or only part of it within the “g”.
This example shows a masked-out underline in two positions.
In the left pair the underline passes through the center of the bowl of the “g”:
the full thickness of the underline shows through the center,
filling it.
In the right pair the underline is slightly lower,
and thus the portion of the underline within the “g” can only show a partial thickness.

Hiding the portion of the underline within the bowl gives a cleaner look to the type, while the curved ends of the underline outside it suggest the continuity of the underline through the letter by hugging its outer contour.

Relatively positioning a descendant moves all text decorations applied to it along with the descendant's text; it does not affect calculation of the decoration's initial position on that line. The 'visibility' property, 'text-shadow', filters, and other graphical transformations likewise also affect all text decorations applied to that box-- including decorations propagated from an ancestor box-- and do not affect the calculation of their initial positions or thicknesses. (In the case of line decorations drawn over an atomic inline or across the margins/borders/padding of a non-replaced inline box, they are analogously associated with the affected atomic inline / non-replaced inline box rather than with the [=decorating box=].)

In the following style sheet and document fragment:

		  blockquote { text-decoration: underline; color: blue; }
		  em { display: block; }
		  cite { color: fuchsia; }

		  <blockquote>
		   <p>
		    <span>
		     Help, help!
		     <em> I am under a hat! </em>

		     <cite> —GwieF </cite>
		    </span>
		   </p>
		  </blockquote>

...the underlining for the blockquote element is propagated to an anonymous inline box that surrounds the span element, causing the text "Help, help!" to be blue, with the blue underlining from the anonymous inline underneath it, the color being taken from the blockquote element. The <em>text</em> in the em block is also underlined, as it is in an in-flow block to which the underline is propagated. The final line of text is fuchsia, but the underline underneath it is still the blue underline from the anonymous inline element. Sample rendering of the above underline example

Sample rendering of the above underline example

This diagram shows the boxes involved in the example above. The rounded aqua line represents the anonymous inline element wrapping the inline contents of the paragraph element, the rounded blue line represents the span element, and the orange lines represent the blocks.

In the following style sheet and document fragment:

		  div { color: black; font-size: 48px; text-decoration: underline; text-shadow: blue 0px 50px 0px; }
		  span { font-size: 20px; vertical-align: top; text-shadow: green 0px 100px 0px; }

                  <div>Help, help! <span>I am under a hat!</span></div>

...the <div> is the [=decorating box=] for its underline (in black), which is rendered uninterrupted through both the <div> and the <span>. Unlike line decorations, however, `text-shadow` is inherited as a property; therefore the green text shadow on the <span> overrides the blue text shadow on the <div>. As a result, when the shadows are painted, the shadow of the <div>’s underline is disjoint across the two elements. Sample rendering of the above underline example

Note: Line decorations are propagated through the box tree, not through inheritance, and thus have no effect on descendants when specified on an element with ''display: contents''.

Text Decoration Lines: the 'text-decoration-line' property

	Name: text-decoration-line
	Value: none | [ underline || overline || line-through || blink ]
	Initial: none
	Inherited: no (but see prose, above)
	Computed value: specified keyword(s)
	Animation type: discrete

Specifies what line decorations, if any, are added to the element. Values have the following meanings:

none: Neither produces nor inhibits text decoration.
underline: Each line of text is underlined.
overline: Each line of text has a line over it (i.e. on the opposite side from an underline).
line-through: Each line of text has a line through the middle.
blink: The text blinks (alternates between visible and invisible). Conforming user agents may simply not blink the text. Note that not blinking the text is one technique to satisfy checkpoint 3.3 of WAI-UAAG. This value is deprecated in favor of Animations [[CSS-ANIMATIONS-1]].

Note: In vertical writing modes, 'text-underline-position' can cause the underline and overline to switch sides. This allows the position of underlines to key off of language-specific preferences automatically.

Text Decoration Style: the 'text-decoration-style' property

	Name: text-decoration-style
	Value: solid | double | dotted | dashed | wavy
	Initial: solid
	Inherited: no
	Computed value: specified keyword
	Animation type: discrete

This property specifies the style of the line(s) drawn for text decoration specified on the element. Values have the same meaning as for the border-style properties [[!CSS-BACKGROUNDS-3]]. ''wavy'' indicates a wavy line. The style of text decorations must remain the same on all decorations originating from a given element, even if descendant boxes have different specified styles.

Text Decoration Color: the 'text-decoration-color' property

	Name: text-decoration-color
	Value: <>
	Initial: currentcolor
	Inherited: no
	Computed value: computed color
	Animation type: by computed value type

This property specifies the color of text decoration (underlines overlines, and line-throughs) set on the element with 'text-decoration-line'. The color of text decorations must remain the same on all decorations originating from a given element, even if descendant boxes have different specified colors.

Text Decoration Shorthand: the 'text-decoration' property

	Name: text-decoration
	Value: <<'text-decoration-line'>> || <<'text-decoration-style'>> || <<'text-decoration-color'>>

This property is a shorthand for setting 'text-decoration-line', 'text-decoration-color', and 'text-decoration-style' in one declaration. Omitted values are set to their initial values. Note: A 'text-decoration' declaration that omits both the 'text-decoration-color' and 'text-decoration-style' values is backwards-compatible with CSS Levels 1 and 2.

The following example underlines unvisited links with a solid blue underline in CSS1 and CSS2 UAs and a navy dotted underline in CSS3 UAs.

			:link {
			  color: blue;
			  text-decoration: underline;
			  text-decoration: navy dotted underline; /* Ignored in CSS1/CSS2 UAs */
			}

Note: The shorthand purposefully omits the 'text-underline-position' property, which is a language/writing-system–dependent setting that keys off the content, so that it can cascade and inherit independently from the (uninherited) stylistic settings of the 'text-decoration' shorthand.

Text Underline Position: the 'text-underline-position' property

	Name: text-underline-position
	Value: auto | [ under || [ left | right ] ]
	Initial: auto
	Inherited: yes
	Computed value: specified keyword(s)
	Animation type: discrete

This property sets the position of an underline specified on the element. (It does not affect underlines specified by ancestor elements.) If ''text-underline-position/left'' or ''text-underline-position/right'' is specified alone, ''text-underline-position/auto'' is also implied.

The following example styles modern Chinese, Japanese, and Korean texts with the appropriate underline positions in both horizontal and vertical text:

			:root:lang(ja), [lang|=ja], :root:lang(ko), [lang|=ko] { text-underline-position: under right; }
			:root:lang(zh), [lang|=zh] { text-underline-position: under left; }

Values have the following meanings:

auto

The user agent may use any algorithm to determine the underline's position; however it must be placed at or under the alphabetic baseline. Note: It is suggested that the default underline position be close to the alphabetic baseline, unless that would either cross subscripted (or otherwise lowered) text or draw over glyphs from Asian scripts such as Han or Tibetan for which an alphabetic underline is too high: in such cases, shifting the underline lower or aligning to the em box edge as described for ''text-underline-position/under'' may be more appropriate.

A typical “alphabetic” underline is positioned just below the alphabetic baseline

under

The underline is positioned [=under=] the element's text content. In this case the underline usually does not cross the descenders. (This is sometimes called “accounting” underline.) This value can be combined with ''text-underline-position/left'' or ''text-underline-position/right'' if a particular side is preferred in vertical typographic modes.

''text-underline-position: under''

Because 'text-underline-position' inherits, and is not reset by the 'text-decoration' shorthand, the following example switches the document to use ''text-underline-position/under'' underlining, which can be more appropriate for writing systems with long, complicated descenders. It is also often useful for mathematical or chemical texts that use many subscripts.

:root { text-underline-position: under; }

Note: The ''text-decoration/under'' value does not guarantee that the underline will not conflict with glyphs, as some fonts have descenders or diacritics that extend below the font’s descent metrics.

left

In vertical typographic modes, the underline is aligned as for ''text-underline-position/under'', except it is always aligned to the left edge of the text. If this causes the underline to be drawn on the "over" side of the text, then an overline also switches sides and is drawn on the "under" side.

right

In vertical typographic modes, the underline is aligned as for ''text-underline-position/under'', except it is always aligned to the right edge of the text. If this causes the underline to be drawn on the "over" side of the text, then an overline also switches sides and is drawn on the "under" side.


''text-underline-position/left''	''text-underline-position/right''

In vertical typographic modes, the 'text-underline-position' values ''text-underline-position/left'' and ''text-underline-position/right'' allow placing the underline on either side of the text. (In horizontal typographic modes, both values are treated as ''text-underline-position/auto''.)

The exact position and thickness of line decorations is UA-defined in this level. However, for underlines and overlines the UA must use a single thickness and position on each line for the decorations deriving from a single [=decorating box=].

A single underline drawn under varying font sizes and vertical positions must be a single line.

vs.

Drawing multiple line segments, each with the position and thickness appropriate to the decorated text, is incorrect.

Correct and incorrect rendering of <u>A<sup>B</sup><big>C</big>D</u>

Note, since line decorations can span elements with varying font sizes and vertical alignments, the best position for a line decoration is not necessarily the ideal position dictated by the [=decorating box=]. For example, an overline positioned to a small font will effectively become a line-through if the element contains text in a significantly larger font-size. Even for underlines, if the text is not aligned to the alphabetic baseline (for example, in vertical typesetting styles, text is aligned by its central baseline by default [[CSS-WRITING-MODES-4]]) an underline will cut through descendant text of a larger font-size. UA consideration of descendant content will therefore result in better typography.

Due to the central baseline alignment of vertical text, a left-side underline on small vertical text will cut through the text of a child with a larger font size. The underline is not allowed to be broken, but adjusting its position further to the left properly accommodates all of the underlined text.

UAs must adjust line positions to match the shifted metrics of [=decorating boxes=] shifted with 'vertical-align' values other than ''vertical-align/baseline'' [[!CSS2]] or subscripted/superscripted via 'font-variant-position' [[!CSS-FONTS-3]], but must not adjust the line position or thickness in response to descendants of a [=decorating box=] that are so styled. This allows superscripts and subscripts to be properly decorated (underlined, struck through, etc.) but prevents them from distorting or breaking the positioning of such decorations on their ancestors.

An underline for just the superscript 'st' in '1st' is drawn just below the superscript,
whereas an underline for the entire text is drawn at the appropriate position for full-size text.

Example of underline applied to superscripted text vs. underline applied to text containing a superscript

Some font formats (such as OpenType) can offer information about the appropriate position of a line decoration. The UA should use such information (such as the underline thickness, or appropriate alphabetic underline position) from the font wherever appropriate. Note: Typically, OpenType font metrics give the position of an ''text-underline-position/alphabetic'' underline; in some cases (especially in CJK fonts), it gives the position of a ''under left'' underline. (In this case, the font's underline metrics typically touch the bottom edge of the em box). The UA may but is not required to correct for incorrect font metrics.

Emphasis Marks

East Asian documents traditionally use small symbols next to each glyph to emphasize a run of text. For example:

Accent emphasis (shown in blue for clarity) applied to Japanese text

The 'text-emphasis' shorthand, and its 'text-emphasis-style' and 'text-emphasis-color' longhands, can be used to apply such marks to the text. The 'text-emphasis-position' property, which inherits separately, allows setting the emphasis marks’ position with respect to the text.

Emphasis Mark Style: the 'text-emphasis-style' property

	Name: text-emphasis-style
	Value: none | [ [ filled | open ] || [ dot | circle | double-circle | triangle | sesame ] ] | <>
	Initial: none
	Applies to: text
	Inherited: yes
	Computed value: the keyword ''text-emphasis-style/none'', a pair of keywords representing the shape and fill, or a string
	Animation type: discrete

This property applies emphasis marks to the element's text. Values have the following meanings:

none: No emphasis marks.
filled: The shape is filled with solid color.
open: The shape is hollow.
dot: Display small circles as marks. The filled dot is U+2022 '•', and the open dot is U+25E6 '◦'.
circle: Display large circles as marks. The filled circle is U+25CF '●', and the open circle is U+25CB '○'.
double-circle: Display double circles as marks. The filled double-circle is U+25C9 '◉', and the open double-circle is U+25CE '◎'.
triangle: Display triangles as marks. The filled triangle is U+25B2 '▲', and the open triangle is U+25B3 '△'.
sesame: Display sesames as marks. The filled sesame is U+FE45 '﹅', and the open sesame is U+FE46 '﹆'.
<>: Display the given string as marks. Authors should not specify more than one [=character=] in <string>. The UA may truncate or ignore strings consisting of more than one grapheme cluster.

If a shape keyword is specified but neither of ''filled'' nor ''open'' is specified, ''filled'' is assumed. If only ''filled'' or ''open'' is specified, the shape keyword computes to ''circle'' in horizontal typographic modes and ''sesame'' in vertical typographic modes. The marks should be drawn using the element's font settings with the addition of the ''font-variant-east-asian/ruby'' feature and the size scaled down 50%. However, since not all fonts have all these glyphs, and some fonts use inappropriate sizes for emphasis marks in these code points, the UA may opt to use a font known to be good for emphasis marks, or the marks may instead be synthesized by the UA. Marks must remain upright in vertical typographic modes: like CJK characters, they do not rotate to match the writing mode. The orientation of marks in horizontal typographic modes of vertical writing modes is undefined in this level (but may be defined in a future level if definitive use cases arise). Note: One example of good fonts for emphasis marks is Adobe's open source Kenten Generic OpenType Font, which is specially designed for the emphasis marks. The marks are drawn once for each typographic character unit. However, emphasis marks are not drawn for:

Word separators or other characters that belong to the Unicode separator classes (Z*). (But note that emphasis marks are drawn for a space that combines with any combining characters.)

Punctuation--specifically, any characters that belong to the Unicode P* general category and do not NFKD normalize [[!UAX15]] to any of the following symbols:

#	U+0023	NUMBER SIGN
%	U+0025	PERCENT SIGN
‰	U+2030	PER MILLE SIGN
‱	U+2031	PER TEN THOUSAND SIGN
٪	U+066A	ARABIC PERCENT SIGN
؉	U+0609	ARABIC-INDIC PER MILLE SIGN
؊	U+060A	ARABIC-INDIC PER TEN THOUSAND SIGN
&	U+0026	AMPERSAND
⁊	U+204A	TIRONIAN SIGN ET
@	U+0040	COMMERCIAL AT
§	U+00A7	SECTION SIGN
¶	U+00B6	PILCROW SIGN
⁋	U+204B	REVERSED PILCROW SIGN
⁓	U+2053	SWUNG DASH
〽️	U+303D	PART ALTERNATION MARK

Characters belonging to the Unicode classes for control codes and unassigned characters (Cc, Cf, Cn).

Note: Control over which characters are marked will be added in Level 4. (The list of punctuation may also be further refined, particularly for non-CJK punctuation.)

Emphasis Mark Color: the 'text-emphasis-color' property

	Name: text-emphasis-color
	Value: <>
	Initial: currentcolor
	Applies to: text
	Inherited: yes
	Computed value: computed color
	Animation type: by computed value type

This property specifies the foreground color of the emphasis marks. Note: ''currentcolor'' keyword computes to itself and is resolved to the value of 'color' after inheritance is performed. This means 'text-emphasis-color' by default matches the text 'color' even as 'color' changes across elements.

Emphasis Mark Shorthand: the 'text-emphasis' property

	Name: text-emphasis
	Value: <<'text-emphasis-style'>> || <<'text-emphasis-color'>>

This property is a shorthand for setting 'text-emphasis-style' and 'text-emphasis-color' in one declaration. Omitted values are set to their initial values.

Note that 'text-emphasis-position' is not reset in this shorthand. This is because typically the shape and color vary, but the position is consistent for a particular language throughout the document. Therefore the position should inherit independently.

Emphasis Mark Position: the 'text-emphasis-position' property

	Name: text-emphasis-position
	Value: [ over | under ] && [ right | left ]?
	Initial: over right
	Applies to: text
	Inherited: yes
	Computed value: specified keyword(s)
	Animation type: discrete

This property describes where emphasis marks are drawn at. If ''[ right | left ]'' is omitted, it defaults to ''text-emphasis-position/right''. The values have following meanings:

over: Draw marks over the text in horizontal typographic modes.
under: Draw marks under the text in horizontal typographic modes.
right: Draw marks to the right of the text in vertical typographic modes.
left: Draw marks to the left of the text in vertical typographic modes.

Emphasis marks are drawn exactly as if each character was assigned the mark as its ruby annotation text with the ruby position given by 'text-emphasis-position' and the ruby alignment as centered. Note that this position may be adjusted if it would conflict with underline or overline decorations. The effect of emphasis marks on the line height is the same as for ruby text.

Note, the preferred position of emphasis marks depends on the language. In Japanese for example, the preferred position is ''over right''. In Chinese, on the other hand, the preferred position is ''under right''. The informative table below summarizes the preferred emphasis mark positions for Chinese and Japanese:

Preferred emphasis mark and ruby position
Language	Preferred position		Illustration
Language	Horizontal	Vertical	Illustration
Japanese	over	right
Korean
Mongolian
Chinese	under	right

If emphasis marks are applied to characters for which ruby is drawn in the same position as the emphasis mark, the emphasis marks are placed outside the ruby. This includes auto-hidden and empty ruby annotations.

Emphasis marks applied to 4 characters, with ruby also on 2 of them

Some editors prefer to hide emphasis marks when they conflict with ruby. In HTML, this can be done with the following style rule:

ruby { text-emphasis: none; }

Some other editors prefer to hide ruby when they conflict with emphasis marks. In HTML, this can be done with the following pattern:

			em { text-emphasis: dot; } /* Set text-emphasis for <em> elements */
			em rt { display: none; }   /* Hide ruby inside <em> elements */

Text Shadows: the 'text-shadow' property

	Name: text-shadow
	Value: none | [ <>? && <>{2,3} ]#
	Initial: none
	Applies to: text
	Inherited: yes
	Computed value: either the keyword ''box-shadow/none'' or
		a list, each item consisting of three absolute lengths
		plus a computed color
	Animation type: as shadow list

This property accepts a comma-separated list of shadow effects to be applied to the text of the element. Values are interpreted as for 'box-shadow' [[!CSS-BACKGROUNDS-3]]. (But note that spread values and the ''box-shadow/inset'' keyword are not allowed.) Each layer shadows the element's text and all its text decorations (composited together). The shadow effects are applied front-to-back: the first shadow is on top. The shadows may thus overlay each other, but they never overlay the text itself. The shadow must be painted at a stack level between the element's border and/or background (if present) and the elements text and text decoration. UAs should avoid painting text shadows over text in adjacent elements belonging to the same stack level and stacking context. (This may mean that the exact stack level of the shadows depends on whether the element has a border or background: the exact stacking behavior of text shadows is thus UA-defined.) It is undefined whether a given shadow layer shadows each glyph or decoration independently or if the text and/or decorations are flattened and then shadowed. Unlike 'box-shadow', text shadows are not clipped to the shadowed shape and may show through if the text is partially-transparent. Like 'box-shadow', text shadows do not influence layout, and do not trigger scrolling or increase the size of the scrollable overflow area. Note: The painting order of shadows defined here is the opposite of that defined in the 1998 CSS2 Recommendation. The ''text-shadow'' property applies to both the ::first-line and ::first-letter pseudo-elements.

Painting Text Decorations

Painting Order of Text Decorations

As in [[!CSS2]], text decorations are drawn immediately over/under the text they decorate, in the following order (bottommost first):

shadows ('text-shadow')
underlines ('text-decoration')
overlines ('text-decoration')
text
emphasis marks ('text-emphasis')
line-through ('text-decoration')

Where line decorations are drawn across box decorations or atomic inlines, they are drawn over non-positioned content and just below any positioned descendants (immediately below layer #8 in CSS2.1 Appendix E).

Overflow of Text Decorations

Text decorations that leak outside a box are considered ink overflow: they do not extend the scrollable overflow area. [[css-overflow-3]]

Appendix A: Acknowledgements

This specification would not have been possible without the help from: Ayman Aldahleh, Bert Bos, Tantek Çelik, Stephen Deach, John Daggett, Martin Dürst, Laurie Anna Edlund, Ben Errez, Yaniv Feinberg, Arye Gittelman, Ian Hickson, Martin Heijdra, Richard Ishida, Masayasu Ishikawa, Michael Jochimsen, Eric LeVine, Ambrose Li, Håkon Wium Lie, Chris Lilley, Ken Lunde, Nat McCully, Shinyu Murakami, Paul Nelson, Chris Pratley, Marcin Sawicki, Arnold Schrijver, Rahul Sonnad, Michel Suignard, Takao Suzuki, Frank Tang, Chris Thrasher, Etan Wexler, Chris Wilson, Masafumi Yabe and Steve Zilles.

Appendix B: Default UA Stylesheet

This appendix is informative, and is to help UA developers to implement default stylesheet, but UA developers are free to ignore or change.


		  /* typical styling of HTML */
		  blink {
		    text-decoration-line: blink;
		  }
		  s, strike, del {
		    text-decoration: line-through;
		  }
		  u, ins, :link, :visited {
		    text-decoration: underline;
		  }
		  abbr[title], acronym[title] {
		    text-decoration: dotted underline;
		  }

		  /* disable inheritance of text-emphasis marks to ruby text:
		    emphasis marks should only apply to base text */
		  rt { text-emphasis: none; }

		  /* set language-appropriate default emphasis mark position */
		  :root:lang(zh), [lang|=zh] { text-emphasis-position: under right; }
		  [lang|=ja], [lang|=ko]     { text-emphasis-position: over right; }

		  /* set language-appropriate default underline position */
		  :root:lang(ja), [lang|=ja],
		  :root:lang(mn), [lang|=mn],
		  :root:lang(ko), [lang|=ko] { text-underline-position: right; }
		  :root:lang(zh), [lang|=zh] { text-underline-position: left;  }
		  /* auto is chosen (implied) above instead of under
		     due to content-compatibility concerns */

If you find any issues, recommendations to add, or corrections, please send the information to www-style@w3.org with [css-text-decor] in the subject line.

While ''text-decoration-line: blink'' can't be fully reproduced with other existing properties, authors can achieve a very similar effect with the following CSS:

			@keyframes blink {
			  0% {
			    visibility: hidden;
			    animation-timing-function: step-end;
			  }
			  25%, 100% {
			    visibility: visible;
			  }
			}
			blink {
			  animation: blink 1s infinite;
			}

Appendix C: Changes

Changes since the August 2019 Candidate Recommendation

Changes include:

Clarify that 'text-shadow' animates as a [=shadow list=] like 'box-shadow'. (Issue 4375)
Be explicit about properties that apply to text. (Issue 5303)
Minor editorial fixes.

Changes since the July 2018 Candidate Recommendation

Changes include:

Clarified that text decoration overflow is ink overflow. (Issue 3272)
Fixed inconsistencies in sample 'text-underline-position' rules. (Issue 3441)
Cleaned up “Computed value” lines to match new conventions.

A Disposition of Comments is available.

Changes since the August 2013 Candidate Recommendation

Significant changes include:

Deferred text-decoration-skip to Level 4 to allow for major changes. Defined behavioral defaults in prose. (Issue 1, Issue 22, Issue 26)
Specified that line-throughs are unaffected by ink-skipping feature. (Issue 24)
Recommended that when ink is skipped, line endings conform to the glyph shape. (Issue 30)
Updated writing-mode–sensitive conditions to depend on typographic mode, to account for addition of ''sideways-lr'' and ''sideways-rl'' values to 'writing-mode' property. Marked orientation of emphasis marks under ''sideways-lr'' and ''sideways-rl'' undefined. (Issue 10, Issue 20)
Made ''[ right | left ]'' option of 'text-emphasis-position' optional, defaulting to ''text-emphasis-position/right''. (Issue 17)
Made 'text-underline-position' imply ''text-underline-position/auto'' instead of ''text-underline-position/under'' when only ''text-underline-position/left'' or ''text-underline-position/right'' is specified. (Issue 18)
Changed text decoration to skip leading and trailing spaces. (Issue 6)
Noted that the positions of ruby annotations may be adjusted to avoid conflicts with text decorations. (Issue 21)
Changed initial value of 'text-shadow' to be currentColor. (Issue 28)
Fixed error in “Computed value” line for 'text-shadow'. (Issue 7)
Fixed canonical order of 'text-shadow' values to match implementations. (Issue 35)
Defined positioning of emphasis marks with respect to auto-hidden and empty ruby annotations. (Issue 9)
If emphasis marks are applied to characters for which ruby is drawn in the same position as the emphasis mark, the emphasis marks are placed outside the ruby. This includes auto-hidden and empty ruby annotations.
Made 'text-emphasis' skip punctuation by default. (Issue 16)
Added rule to apply ''font-variant-east-asian/ruby'' to emphasis marks' font. (Issue 13)
Various corrections and improvements to the default UA rules for 'text-emphasis-position' and 'text-underline-position'. (Issue 11, Issue 12, Issue 18, Issue 19, Issue 36)

Privacy Considerations

No new privacy considerations have been reported on this specification.

Security Considerations

No new security considerations have been reported on this specification.